This invention relates to a flexible gear coupling for connecting a drive electric motor and a speed reduction gear unit of a railway vehicle.
In a railway vehicle, the drive motor is mounted to a bogie frame and the speed reduction gear unit is mounted to an axle. Therefore, axes of the output shaft of the drive electric motor and the pinion shaft of the speed reduction gear unit come out of alignment due to shaking of the travelling vehicle, generating a flexure in the shafts. The flexible gear coupling is connected between the drive electric motor and the speed reduction gear unit so that the smooth power transmission can be achieved between these shafts even when the shafts are out of alignment as discussed above.
FIG. 5 is a front view showing in partial section a part of structure of the conventional flexible gear coupling described in Japanese Utility Model Publication No. 35-13707 for example, FIG. 6 is a sectional view showing the structure of the main portion of the flexible gear coupling shown in FIG. 5, FIG. 7 is a sectional view showing the state in which the axis of the rotating shaft shown in FIG. 6 is displaced in the perpendicular direction with respect to the axis of the sleeve and a flexure is generated, and FIG. 8 is a sectional view showing the state in which a larger flexure is generated as compared to the state shown in FIG. 7.
In the figures, the reference numerals 1 are rotary shafts, one of them being an output shaft of a drive electric motor for example and the other being an input shaft to a speed reduction gear unit. 2 are sleeves fastened together by bolts or the like into a unitary structure, each having an inner teeth gear 2a formed in an end portion inner circumferential surface. 3 is a pair of pinions each secured at its inner circumference side to the respective rotary shaft 1 and having on an outer circumference side an outer teeth gear 3a to which the crowning is applied for engaging with the inner teeth gear 2a of the sleeves 2 and having in an outer side surface a recessed portion 3b open toward the outside. Grease (not shown) is filled into the space in which the inner teeth gear 2a of the sleeve 2 and the outer teeth gear 3a engage with each other. 4 are end covers, each having one end secured to the sleeve 2 and the other end disposed at a position within the recessed portion 3b of the pinion 3 with a predetermined clearance therebetween for preventing the grease within the sleeve 2 from scattering out and for preventing the ingress of dust particles. 5 are annular elastic seal members secured to the rotary shaft 1 and urged against the other side of the end cover 4 for preventing any dust particles from entering through the gap between the pinion 3 and the end cover 4.
In the conventional flexible gear coupling having a structure as above described, even when the vehicle body shakes during travelling and the axes of the output shaft of the driving electric motor and the input shaft of the speed reduction gear unit come out of alignment, since the outer teeth gear 3a of the pinion 3 is crowned, the transmission of the driving force from on rotary shaft 1 to the other rotary shaft 1 is smoothly achieved and, even when both of the rotary shafts 1 shift in the axial direction, the outer teeth gear 3a of the pinion 3 freely move along the grooves of the inner teeth gear 2a of the sleeve 2. Further, in the state in which both of the rotary shafts 1 are aligned on a common axis, the seal member 5 is urged at a predetermined pressure against the other end of the end cover 4 over the entire circumference thereof thereby establishing a good seal.
Since the conventional flexible gear coupling has a structure as above-described, the seal member 5 experiences an excessive deformation as shown in FIG. 7 when a flexure is generated, posing a problem that the seal member is easily worn and damaged. Also, when the flexure further progresses, a gap 6 generates between the end cover 4 and the seal member 5 as shown in FIG. 8, making the ingress of dust particles easier. Further, since the rotational speed of the driving electric motor is very high and may be 6,000 rpm for example, the life of the seal member is shortened by wearing and the sealing may be damaged by the centrifugal force.